Electro-optical module

ABSTRACT

The electro-optical module has a substrate with a mounting surface that is free from depressions. A surface-mounted component unit is disosed on the mounting surface. The component unit contains as integral components an electro-optical component and a lens which are aligned directly with one another. The surface serves, furthermore, as a reference plane for assembling a receptacle for an optical fiber plug.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of copending International ApplicationPCT/DE97/01041, filed May 16, 1997, which designated the United States.

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION

The invention is in the field of electro-optical structures for opticalsystems. In particular, the invention pertains to an electro-opticalmodule having an electro-optical component and having a receptacle foran optical fiber plug, which are arranged on a single surface of asubstrate, and having a lens arranged in the optical path between thecomponent and the receptacle.

Such modules are utilized in the transmission of signals by means ofoptical fibers, and contain at least one component which comprises anelectro-optical transducer. An electro-optical transducer serves toconvert optical signals into electrical signals and/or, conversely, toconvert electrical signals into optical signals.

A module of the above-mentioned type has become known from U.S. Pat. No.5,337,398 (European EP 0 600 645 A1) to Benzoni et al. That modulecomprises two electro-optical components (laser diode and photodiode)which are positioned on metal surfaces (pads) precisely placed on asilicon substrate by means of a reheatable solder. When the solder issubsequently reheated (i.e., reflow), the components are centered withrespect to the pads because of the surface tension of the liquefiedsolder.

A multiplicity of alignment depressions are produced in the siliconmaterial by etching into the surroundings of the pads, and thus in thesurroundings of the electro-optical components. It is possible to insertinto the depressions aligning elements—for example, aligning balls—whichcooperate with corresponding aligning depressions in a separate carrierwhich is to be aligned precisely via the respective electro-opticalcomponent.

The carrier can carry a lens provided in the beam path between thecomponent and a receptacle for an optical fiber plug, or can align thereceptacle directly with respect to the components.

If the individual parts are produced with extreme precision, inparticular the carrier, the bipartite aligning depressions and, ifappropriate, the lens and/or the receptacle for the optical fiber plug,then the prior art module renders it possible to dispense with an activeadjustment of the receptacle with respect to the electro-opticalcomponent. The height of the carrier and, if applicable, the lensdiameter are, however, design variables, which exert a considerableinfluence on the relative position of the receptacle and/or of theoptical fiber plug with respect to the electro-optical component in theZ-direction. The Z-direction is the orientation of the optical fiber orthe direction of the beam path. The direct fastening, addressed in U.S.Pat. No. 5,337,398 (EP 0 600 645 A1), of the receptacle on the substratesurface can then lead to component strains when the geometry of thecarrier and, if applicable, of the lens does not permit the actualpositioning of the receptacle in the Z-direction to be connecteddirectly without strain to the substrate.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide anelectro-optical module, which overcomes the above-mentioneddisadvantages of the heretofore-known devices and methods of thisgeneral type and which has highly precise, reproducible couplinggeometries in the Z-direction with as few individual parts as possible.

With the foregoing and other objects in view there is provided, inaccordance with the invention, an electro-optical module, comprising:

-   -   a substrate formed with a mounting surface;    -   a receptacle for an optical fiber plug defining a beam path        substantially perpendicular to the mounting surface; and    -   an integrated component unit mounted on the mounting surface,        the component unit comprising an electro-optical component and a        lens directly aligned with one another in the beam path between        the electro-optical component and the receptacle. It is        advantageous, thereby, that it is no longer necessary to provide        the mounting surface with aligning structures.

In other words, the objects of the invention are satisfied with anelectro-optical module of the type mentioned in the introduction thathas a mounting surface free of aligning structures, and wherein theelectro-optical component and the lens are aligned directly with oneanother, forming an integrated component unit that can be assembled onthe surface.

From a production engineering standpoint, a substantial advantage of theinvention consists in that—apart from conductor tracks andmetallizations—the surface of the substrate can remain unstructured andfree from depressions. Consequently, the selection of the material forthe substrate is not dependent on special structuring properties—suchas, for example, in the case of the silicon substrate to be used inaccordance with the above-mentioned U.S. Pat. No. 5,337,398. Rather, thesubstrate (for example, printed circuit board) can be selected in anoptimum fashion in accordance with aspects of handling, productionengineering and, in particular, costs.

A further substantial advantage of the invention consists in the factthat the surface-mountable component unit formed by the electro-opticalcomponent and the lens can be produced and tested in advance in a highlyprecise fashion. Subsequent assembly, affected by tolerances, of a lenssupport via an electro-optical component which is to be assembled inadvance on the substrate is not required with the novel module.Consequently, both production engineering is simplified and anadditional tolerance variable is excluded. The component unit canpreferably have metallic surfaces for direct electrical contact with thesubstrate. The reproducible accuracy in the Z-direction is determinedonly by the component unit, while the substrate thickness is quiteirrelevant in this regard.

In accordance with an added feature of the invention, the receptacle isdisposed so as not to touch the component unit, the receptacle makingcontact with and being connected substantially only to the mountingsurface of the substrate. This feature permits an embodiment that iscompletely free from strain and is scarcely stressed in the case oftemperature variations.

In accordance with an additional feature of the invention, there isprovided an electronic circuit on a surface of the substrate that isaverted from the receptacle. Consequently, an electronic drive circuit(in the state of transmission) or a receiving or amplifying circuit canbe arranged very near to the component. The signal paths are therebyshortened, and the vulnerability of the system is reduced.

In accordance with another feature of the invention, a cap is attacheddirectly to the mounting surface of the substrate for electricallyshielding the component unit. This feature is particularly important tofurther improve the radiofrequency properties and the insensitivity toexternal disturbances.

In accordance with a concomitant feature of the invention, the substrateforms a part of a rigid-flexible-rigid circuit carrier.

The design engineering is thereby simplified. Mechanical and electricalconnections are united by design in the flexible part of therigid-flexible-rigid circuit carrier.

Other features which are considered as characteristic for the inventionare set forth in the appended claims.

Although the invention is illustrated and described herein as embodiedin an electro-optical module, it is nevertheless not intended to belimited to the details shown, since various modifications and structuralchanges may be made therein without departing from the spirit of theinvention and within the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however,together with additional objects and advantages thereof will be bestunderstood from the following description of specific embodiments whenread in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a longitudinal section through a moduleaccording to the invention;

FIG. 2A is an enlarged plan view of the component unit of FIG. 1;

FIG. 2B is a sectional view of the component unit; and

FIG. 3 is a partial perspective view of the substrate as part of arigid-flexible-rigid circuit carrier.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the figures of the drawing in detail and first,particularly, to FIG. 1 thereof, there is seen an electro-optical modulewith a substrate in the form of a printed circuit board 1. Among othercomponents, the PCB 1 carries on its front flat side (first surface) 2an electro-optical component 3. Indicated on the rear surface 4 of thesubstrate 1 are individual electronic components 5, 6 which areinterconnected via conductor tracks 7, and are connected to connectorpads 8, 9 on the first surface 2 by means of electric bushings (notrepresented in more detail) through the substrate 1. The connector padsserve to make contact with the electro-optical component 3. A flange 10of a receptacle 12 is supported on the same surface 2. The flange 10 isformed with a central bore 14 for receiving an optical fiber plug (notillustrated in more detail for reasons of clarity). Upon insertion, theend face of the plug comes to bear against a partition 16 with a centralbore 17 which defines an optical path between the electro-opticalcomponent 3 and an optical fiber end held centrally in the optical fiberplug. As will become clear from the following, more detailedexplanation, the component 3 forms an integral component of a componentunit 20 mounted on the surface 2 of the substrate 1.

The top side 22, remote from the substrate, of the component unit 20 isshaped as a lens (compare FIG. 2), which is thus situated in the opticalpath between the component and the receptacle 12. The surface 2 has thepads 8, 9, and is otherwise not structured mechanically; in particular,it includes no aligning depressions for the component unit 20.

As FIG. 2 shows in plan view (FIG. 2A) and in a sectional representation(FIG. 2B), the component unit 20 is an integrated unit of a lens 28,constructed on the top side 22, and an electro-optical component 3. Forthe purpose of protection against external influences, the component 3is embedded in a hermetically tight fashion in a filling compound 30which also includes a bond wire 32 provided for contacting the component3 on the top side thereof. As illustrated in FIG. 2A, the bond wire 32leads to a connecting metallization 34 which extends over a bevel andthe base region of a depression 40 holding the component 3. Theunderside of the component 3 is connected in an electrically conductingfashion to a second metallization 42. When the component unit 20 ismounted on the surface 2, the outer metallization regions 34a, 42a makecontact with the corresponding connector pads on the substrate. Thistype of contacting is known as surface mounting.

Referring again to FIG. 1, the receptacle 12 is arranged so as not totouch with respect to the component unit 20, and makes contact with andis connected to only the surface 2 of the substrate 1. It is possiblethereby to achieve a design of the module which is particularly low instrain and is insensitive to temperature changes. Also to be seen is anelectrically conducting cap 60 which is attached directly to the surface2 and by means of which the component unit 20 is electrically screenedon the receptacle side.

In the described module, although there may be a need to adjust thereceptacle 12 with respect to the component 3 in the X-Y direction—thatis to say in the plane perpendicular to the Z-direction—this adjustmentis not a problem, because of the smooth surface 2, of planarconstruction, of the printed circuit board. The module offers thesubstantial advantage that only comparatively few tolerances influencethe accuracy in the Z-direction, with the result that in this regard noadjusting or correcting measures remain necessary after assembly. Afurther advantage of the module is that the component unit 20 and thereceptacle 12 are aligned in the Z-direction with the same referencesurface—specifically, the surface 2. The accuracy in the Z-direction isthereby essentially determined only by a single part, i.e., thecomponent unit 20. The substrate thickness, on the other hand, has nobearing. The evaluation or drive electronics for the component 3 canadvantageously be arranged on the rear side of the substrate. Favorableradio-frequency properties and a high insensitivity to externaldisturbances are ensured by short conductor tracks 7 and directplated-through holes to the component unit 20. The insensitivity isfurther increased by the cap 60, with which contact is correspondinglymade.

With reference to FIG. 3, the perspective view shows arigid-flexible-rigid circuit carrier 50. The combination comprises arigid part 1, formed by the substrate, a flexible part 51 with flexibleconductors and a further rigid part 52. The circuit carrier 50 can bemounted as a unit during assembly. The result is substantially improvedeconomy with regard to production fastening steps.

We claim:
 1. An electro-optical module, comprising: a substrate formedwith a mounting surface; a receptacle for an optical fiber plug defininga beam path substantially perpendicular to said mounting surface; and anintegrated component unit mounted on said mounting surface, saidcomponent unit comprising an electro-optical component and a lensdirectly aligned with one another in the beam path between saidelectro-optical component and said receptacle.
 2. The electro-opticalmodule according to claim 1 7, wherein said mounting surface issubstantially free from aligning structures.
 3. The electro-opticalmodule according to claim 1 7, wherein the receptacle is disposed so asnot to touch said component unit, said receptacle making contact withand being connected substantially only to said mounting surface of saidsubstrate.
 4. The electro-optical module according to claim 1 7, whereinsaid substrate has a second surface on a side thereof averted from saidreceptacle, and including an electronic circuit carried on said secondsurface.
 5. The electro-optical module according to claim 1 7, whichfurther comprises a cap attached directly to said mounting surface ofsaid substrate for electrically shielding said component unit.
 6. The Arigid-flexible-rigid circuit carrier comprising: the electro-opticalmodule according to claim 1 7, wherein said substrate forms a part of arigid-flexible-rigid circuit carrier first rigid part; a flexible partcomprising flexible conductors connected to the substrate; and a secondrigid part comprising a printed circuit board.
 7. An electro-opticalmodule, comprising: a substrate formed with a mounting surface; areceptacle for an optical fiber plug defining a beam path substantiallyperpendicular to said mounting surface; and an integrated component unitmounted on said mounting surface, said integrated component unitcomprising: a solid body defining at least first and second surfaces; anelectro-optical component mounted on the first surface; and a lensformed on the second surface, wherein the lens and the electro-opticalcomponent are directly aligned with one another in the beam path betweensaid electro-optical component and said receptacle, wherein said firstsurface is opposite said second surface.
 8. The electro-optical moduleaccording to claim 7, wherein said first surface is substantiallyparallel to said second surface.
 9. The electro-optical module accordingto claim 7, wherein said first surface is substantially parallel to saidmounting surface.
 10. The electro-optical module according to claim 7,wherein said electro-optical component is embedded in a fillingcompound.
 11. The electro-optical module according to claim 10, furthercomprising a bond wire partially embedded in said filling compound, saidbond wire forming at least a portion of an electrical connection betweensaid electro-optical component and said substrate.
 12. Anelectro-optical module, comprising: a substrate formed with a mountingsurface; a receptacle for an optical fiber plug defining a beam pathsubstantially perpendicular to said mounting surface; and an integratedcomponent unit mounted on said mounting surface, said integratedcomponent unit comprising: a solid body defining at least first andsecond surfaces; an electro-optical component mounted on the firstsurface; and a focusing lens formed on the second surface, wherein thelens and the electro-optical component are directly aligned with oneanother in the beam path between said electro-optical component and saidreceptacle.
 13. The electro-optical module according to claim 12,wherein the solid body further defines a depression on the first surfacein which the electro-optical component is mounted.
 14. Theelectro-optical module according to claim 12, wherein the receptacleincludes a partition and wherein, upon insertion of the optical fiberplug, the partition is disposed between an end face of the optical fiberplug and the lens.
 15. An electro-optical module, comprising: asubstrate formed with a mounting surface; a receptacle for an opticalfiber plug defining a beam path substantially perpendicular to saidmounting surface; and an integrated component unit mounted on saidmounting surface, said integrated component unit comprising: a lenscomponent on which a lens is formed; an electro-optical componentdirectly aligned with the lens in the beam path between saidelectro-optical component and said receptacle; and a first metallizationextending over a portion of the lens component and connected in anelectrically conducting fashion to the electro-optical component and toa first corresponding connector pad on the mounting surface of thesubstrate.
 16. The electro-optical module according to claim 15, whereinthe first metallization is electrically connected to an underside of theelectro-optical component facing the lens.
 17. The electro-opticalmodule according to claim 15, wherein said integrated component unitfurther comprises a second metallization extending over a portion of thelens component and connected in an electrically conducting fashion tothe electro-optical component and to a second corresponding connectorpad on the mounting surface of the substrate.
 18. The electro-opticalmodule according to claim 17, wherein the second metallization iselectrically connected to the electro-optical component via a bond wire.